The hypothesis is that RSVIG-IV is safe and can prevent respiratory syncytial virus associated hospitalizations in young children with heart disease when given monthly during the RSV season. The objectives are to confirm that passive immunization with high dose RSVIG-IV will prevent or modify the course of RSV disease in this population and to assess the safety of monthly 750 mg/kg infusions of RSVIG-IV in larger numbers of children with heart disease. This study has been completed.